Crazy Stone computer Go program defeats Ishida Yoshio 9 dan with 4 stones 12 years ago
I'm around 2000 ELO in chess and I'd win every single game vs anyone with 4 pawns or a minor piece handicap. Being a single pawn up is usually decisive in chess. Having said that, this whole discussion is pointless, no one ever gives handicaps in chess, because it completely messes up the initial position. Even lacking one or two pawns at start will make it extremely hard to establish any kind of central presence.
edit: Apparently kasparov gave a ~2200 guy 2 pawn handicap once, ended up winning 2.5-1.5 http://www.telegraph.co.uk/news/uknews/1317037/Kasparov-make....